This is a law site, but many of us see baseball as a metaphor for much of life, so on his historic occasion (or at least the day after), I hope you will indulge my brief reverie.
When contemplating the most hallowed record in all of American team sports, it is interesting to reflect on the fact that Babe Ruth held the lifetime major league home run record for 53 years, and then Hank Aaron held it for 33 years more, but Barry Bonds may enjoy being the record-holder for less than 10 years. Neither Ruth nor Aaron had a legitimate challenger so close to their home run totals at such a young age as Alex Rodriguez is to Bonds' newly-minted record.
Although Lou Gehrig was only 32 years old when Ruth retired, he was 326 home runs behind Ruth at the time, and was fated to play for only three more seasons before being fatally stricken with ALS. Both Jimmy Foxx and Mel Ott were in their mid-to-late 20s, but each was more than 400 home runs behind Ruth and thus too far removed to be considered a serious challenger to his record at that time.
Willie Mays was only 53 home runs behind Aaron at the close of the 1973 season, but that was his last season while Aaron played three more years and broke Ruth's record in the Braves' fourth game of the 1974 campaign. When Aaron became the all-time home run champion in April 1974, Harmon Killebrew and Frank Robinson were at the end of their careers and each was more than 130 home runs behind Aaron. Willie McCovey was 36 years of age at the time and had barely more than 400 home runs in his career (he would finish a few years later with 521).
By contrast, A-Rod is 32 years old and already has hit 500 home runs. He will need to amass around 280 more home runs, give or take a few, in the remainder of his career to wrest the home run title from Bonds. That is no sure thing to hit 40 home runs a year for 7 more years as he is approaching 40 years of age. In fact, in the history of baseball, only two men have accomplished the feat of hitting 40 or more home runs in a season that ended after their 39th birthday -- Aaron once and Bonds twice. But neither would I bet against A-Rod, the undisputed heir apparent.
One final note that has been lost for many to the dim mists of history. Ruth became the all-time home run king in 1921, at the very beginning of his Yankee career as an everyday player, when he hit his 132nd career home run. The old record was held by Hall of Fame first baseman Roger Connor who played in the last two decades of the 19th Century for the National League team in New York, the Gothams. By virtue of Connor's great stature surpassing 6 foot 3 inches and 200 pounds, the New York Gothams became forever more known as the Giants. Connor, who is now credited by modern baseball researchers with 138 career home runs, held the lifetime home run record for more than 25 years.